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Old 01-02-2009, 03:05 PM   #24 (permalink)
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Originally Posted by NeilBlanchard View Post

I've attempted to show the air flow lines, overlaid on the "velocity" image (if that is what it is showing):

And here it is with just the flow lines:

As you can see the greatest velocity occurs where the air is being pushed aside at the greatest angle, and this is what gives it the greatest velocity. I think that the nose pushes the air up above the main part of the hood, and then the upper part of the windshield again pushes it up; creating another higher velocity zone.
Neil,I think a smoke-rake image of the car would better show how the body deforms the airflow.I think the car is a Porsche 944,and I've seen imagery from Porsche,and it's a little different.------------------------------- To illustrate "lift" associated from velocity,I've gleaned the following: In the windtunnel development of Sunraycer,too much air went under the car,causing negative lift under the very long,cantilevered tail.The "lift" would pull the tail down,causing the nose to lift.Fairings behind the wheels would catch the air and yaw the car sideways,and then the car would liftoff,flying.This was at 20-mph(32 km/h).For the World Solar Challenge,the nose was re-configured and wheel fairings deleted,trading increased drag for better stability.-------------------------- A 1969 Z-28 Camaro was tested and found to generate 500-pounds(227-kg) of lift at the nose at 128-mph(206 km/h).Addition of a chin spoiler cut lift to 275-lbs (125kg).-------------------------- A half-million pound (227,272 kg) Boeing 747 leaves the ground at 165-mph (266-km/h).------------------------------- Racing Beat's 3,000-lb (1,363 kg)Mazda RX-7 LSR car "flew" at 235-mph ( 379 km/h),landing on it's roof at Bonneville.-------------------------- In 1989,Art Arfon's "Green Monster #27" ( which looks like the fuselage of a 1951 Grumman F-9F-2 Panther ) took off at 300-mph (484 km/h),did a complete flip,landed on it's side after 300 feet in the air,grinding to a halt after a half-mile(0.8 km) on Bonneville's salt.----------------------------------- Lastly,during the Monte Carlo Grand Prix,when the Formula-1 cars go through the tunnel at Monaco,they experience oversteer,do to the ceiling of the tunnel,20-feet overhead.It's been found that the rear wing can suffer lift losses from any disturbance within up to about 30-feet.Using inverted logic,one can deduce that an F-1 car disturbs the air up to 30-feet away.---------------------------- If windtunnels were much larger than they are,we could better appreciate how much our cars really affect the air around them due to "lift" and the implications with respect to mpg.
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